Water-Based Ink for Ink-Jet Recording, Ink Cartridge, Ink-Jet Recording Apparatus and Method of Stabilizing Water-Based Ink for Ink-Jet Recording

ABSTRACT

A water-based ink for ink-jet recording includes a coloring agent and water. The coloring agent includes a dye represented by the following general formula (1). In the ink, an amount of glycerin is set so as to satisfy the following condition (A). 
       3.5 X −5≦ Y 1≦3.5 X   (A)
         X: an amount of a dye represented by general formula (1) relative to a total amount of the ink (wt %)   Y1: an amount of glycerin relative to a total amount of the ink (wt %)

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 12/342,771, filedDec. 23, 2008, the disclosure of which is hereby incorporated byreference. This application claims priority from Japanese PatentApplication Nos. 2007-338536 and 2007-338539 filed on Dec. 28, 2007. Theentire subject matter of the Japanese Patent Applications isincorporated herein by reference.

BACKGROUND

Conventionally, as an ink for ink-jet recording, an ink is known thatcontains dye, ethylene glycol, glycerin, and the like. The ink isrequired to be (i) not deteriorated in prolonged storage and good inpreservation stability, (ii) not aggregated due to contact with apigment ink even in a case where the ink is used in combination with thepigment ink in an ink-jet recording apparatus and good in ejectionstability, and (iii) good in toughness such as light resistance andozone resistance of a recording material. However, there were noconventional inks that satisfy all of the aforementioned performances.

SUMMARY

A first water-based ink for ink-jet recording is a water-based ink forink-jet recording comprising a coloring agent and water. The coloringagent comprises a dye represented by the following general formula (1).In the ink, an amount of glycerin is set so as to satisfy the followingcondition (A).

3.5X−5≦Y1≦3.5X  (A)

-   -   X: an amount of a dye represented by general formula (1)        relative to a total amount of the ink (wt %)    -   Y1: an amount of glycerin relative to a total amount of the ink        (wt %)

wherein in the general formula (1),R₁, R₂, Y₁, and Y₂ each represents a monovalent group, provided that R₁,R₂, Y₁, and Y₂ may be the same or different;X₁ and X₂, each independently, represents an electron attractive group,provided that X₁ and X₂ may be the same or different;Z₁ and Z₂, each independently, represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted alkynyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that Z₁and Z₂ may be the same or different; andM represents a hydrogen atom, or a cation.

The X and Y1 may strictly satisfy the condition (A) or may be placed atneighborhood of the straight line of Y1=3.5X−5 in Y1<3.5X−5 and thestraight line of Y1=3.5X in Y1>3.5X.

A second water-based ink for ink-jet recording is a water-based ink forink-jet recording comprising a coloring agent and water. The coloringagent comprises a dye represented by the general formula (1). In theink, an amount of ethylene glycol is set so as to satisfy the followingcondition (D).

3.5X−5≦Y2≦X+10  (D)

X: an amount of a dye represented by general formula (1) relative to atotal amount of the ink (wt %)Y2: an amount of ethylene glycol relative to a total amount of the ink(wt %)

The X and Y2 may strictly satisfy the condition (D) or may be placed atneighborhood of the straight line of Y2=3.5X−5 in Y2<3.5X−5 and thestraight line of Y2=X+10 in Y2>X+10.

An ink cartridge comprises the first or the second water-based ink forink-jet recording.

An ink-jet recording apparatus comprises the ink cartridge and an inkejection unit. The water-based ink for ink-jet recording comprised inthe ink cartridge is ejected from the ink ejection unit.

A method of stabilizing a first water-based ink for ink-jet recording isa method of stabilizing a water-based ink for ink-jet recordingcomprising a coloring agent and water. The coloring agent comprises adye represented by the general formula (1). The ink is stabilized bysetting an amount of glycerin so as to satisfy the condition (A) in theink.

A method of stabilizing a second water-based ink for ink-jet recordingis a method of stabilizing a water-based ink for ink-jet recordingcomprising a coloring agent and water. The coloring agent comprises adye represented by the general formula (1). The ink is stabilized bysetting an amount of ethylene glycol so as to satisfy the condition (D)in the ink.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view showing a construction of anexample of an ink-jet recording apparatus.

FIG. 2 is a view for explaining a method of an aggregation evaluation inExamples of the present invention.

FIG. 3 is a graph indicating a relationship between an amount of a dyerepresented general formula (1) [X (wt %)] and an amount of glycerin [Y1(wt %)] relative to the total amount of ink in Examples 1 to 9 andComparative Examples 1 to 11.

FIG. 4 is a graph indicating a relationship between an amount of a dyerepresented general formula (1) [X (wt %)] and an amount of ethyleneglycol [Y2 (wt %)] relative to the total amount of ink in Examples 10 to18 and Comparative Examples 12 to 19.

DETAILED DESCRIPTION

With respect to the first water-based ink for ink-jet recording, in acase of X>5/3.5, glycerin may be comprised in the first water-based inkfor ink-jet recording in an amount satisfying the condition (A), and ina case of X≦5/3.5, glycerin may be comprised in the water-based ink inan amount satisfying the following condition (B).

0<Y1≦3.5X  (B)

X: an amount of a dye represented by general formula (1) relative to atotal amount of the ink (wt %)Y1: an amount of glycerin relative to a total amount of the ink (wt %)

In the case of X≦5/3.5, the X and Y1 may strictly satisfy the condition(B) or may be placed at neighborhood of the straight line of Y1=3.5X inY1>3.5X.

With respect to the first water-based ink for ink-jet recording, in acase of X≦5/3.5, glycerin may not be comprised in the first water-basedink for ink-jet recording. In this manner, in a case where an amount ofa dye represented by the general formula (1) is small, a water-based inkmay be obtained that is good in ejection stability and hardly generatesthe aggregation even when glycerin is not comprised.

The first water-based ink for ink-jet recording further may satisfy thefollowing condition (C).

(C) an amount of a dye represented by general formula (1) exceeds 0 wt %and is equal to or less than about 7 wt % relative to a total amount ofthe ink

With respect to the second water-based ink for ink-jet recording, in acase of X>5/3.5, ethylene glycol may be comprised in the secondwater-based ink for ink-jet recording in an amount satisfying thecondition (D), and in a case of X≦5/3.5, ethylene glycol may becomprised in the water-based ink in an amount satisfying the followingcondition (E).

0<Y2≦X+10  (E)

X: an amount of a dye represented by general formula (1) relative to atotal amount of the ink (wt %)Y2: an amount of ethylene glycol relative to a total amount of the ink(wt %)

In the case of X≦5/3.5, the X and Y2 may strictly satisfy the condition(E) or may be placed at neighborhood of the straight line of Y2=X+10 inY2>X+10.

With respect to the second water-based ink for ink-jet recording, in acase of X≦5/3.5, ethylene glycol may not be comprised in the secondwater-based ink for ink-jet recording. In this manner, in a case wherean amount of a dye represented by the general formula (1) is small, awater-based ink may be obtained that is good in ejection stability andhardly generates the aggregation even when ethylene glycol is notcomprised.

The second water-based ink for ink-jet recording further may satisfy thefollowing condition (F).

(F) an amount of a dye represented by general formula (1) exceeds 0 wt %and is equal to or less than about 6 wt % relative to a total amount ofthe ink

Application of the first and the second water-based ink for ink-jetrecording is not particularly limited and, for example, may be used as awater-based yellow ink. The first and the second water-based ink forink-jet recording may be used as a water-based ink other than a yellowcolor by further comprising coloring agents other than the dyerepresented by the general formula (1).

Next, the first water-based ink for ink-jet recording (hereinafter, alsomay simply be referred to as “first water-based ink” or “first ink”) isexplained. The first water-based ink comprises a coloring agent andwater. As described above, the coloring agent comprises the dyerepresented by the general formula (1).

In the general formula (1), R₁, R₂, Y₁, and Y₂ each represents amonovalent group, provided that R₁, R₂, Y₁, and Y₂ may be the same ordifferent. The monovalent group is a hydrogen atom, or a monovalentsubstituent. Examples of the monovalent substituent include a halogenatom, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenylgroup, an alkynyl group, an aryl group, a heterocyclic group, a cyanogroup, a hydroxyl group, a nitro group, an alkoxy group, an aryloxygroup, a silyloxy group, a heterocyclic oxy group, an acyloxy group, acarbamoyloxy group, an alkoxy carbonyloxy group, an aryloxy carbonyloxygroup, an amino group, an amido group, an acylamino group, an ureidogroup, an amino carbonyl amino group, an alkoxy carbonyl amino group, anaryloxy carbonyl amino group, a sulfamoyl amino group, an alkyl sulfonylamino group, an aryl sulfonyl amino group, an alkyl thio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, an alkylsulfinyl group, an aryl sulfinyl group, an alkyl sulfonyl group, an arylsulfonyl group, an acyl group, an aryloxy carbonyl group, an alkoxycarbonyl group, a carbamoyl group, a phosphino group, a phosphinylgroup, a phosphinyloxy group, a phosphinyl amino group, a silyl group,an azo group, an imido group and the like. Each may further have amonovalent substituent. Out of these, preferred is a hydrogen atom, ahalogen atom, an alkyl group, an aryl group, a heterocyclic group, acyano group, an alkoxy group, an amido group, an ureido group, an alkylsulfonyl amino group, an aryl sulfonyl amino group, a sulfamoyl group,an alkyl sulfonyl group, an aryl sulfonyl group, a carbamoyl group, oran alkoxy carbonyl group. Particularly, a hydrogen atom, an alkyl group,an aryl group, a cyano group, or an alkyl sulfonyl group is preferred.

The halogen atom is a chlorine atom, a bromine atom, or an iodine atom.Out of these, a chlorine atom, or a bromine atom is preferred.

The alkyl group includes a substituted or unsubstituted alkyl group. Thesubstituted or unsubstituted alkyl group may be an alkyl group having 1to 30 carbon atoms. Examples of the alkyl group include a methyl group,an ethyl group, a butyl group, a t-butyl group, an n-octyl group, aneicosyl group, a 2-chloroethyl group, a hydroxyethyl group, a cyanoethyl group, a 4-sulfobutyl group and the like. As the examples of thesubstituent of the substituted alkyl group include a straight chain orbranched alkyl group having 1 to 12 carbon atoms such as a methyl group,an ethyl group, a propyl group, an isopropyl group, a sec-butyl group, at-butyl group, a 2-ethylhexyl group, a 2-methyl sulfonyl ethyl group, a3-phenoxypropyl group, a trifluoromethyl group and the like; a straightchain or branched aralkyl group having 7 to 18 carbon atoms; a straightchain or branched alkenyl group having 2 to 12 carbon atoms; a straightchain or branched alkynyl group having 2 to 12 carbon atoms; a straightchain or branched cycloalkyl group having 3 to 12 carbon atoms such as acyclopentyl group and the like; a straight-chain or branchedcycloalkenyl group having 3 to 12 carbon atoms; a halogen atom such as achlorine atom, a bromine atom and the like; an aryl group such as aphenyl group, a 4-t-butylphenyl group, a 2,4-di-t-amyl phenyl group andthe like; a heterocyclic group such as an imidazolyl group, a pyrazolylgroup, a thoriazolyl group, a 2-furyl group, a 2-thienyl group, a2-pyrimidinyl group, a 2-benzothiazolyl group and the like; a cyanogroup; a hydroxyl group; a nitro group; a carboxy group; an amino group;an alkoxy group such as a methoxy group, an ethoxy group, a2-methoxyethoxy group, a 2-methyl sulfonyl ethoxy group and the like; anaryloxy group such as a phenoxy group, a 2-methyl phenoxy group, a4-t-butyl phenoxy group, a 3-nitro phenoxy group, a 3-t-butyloxycarbonyl phenoxy group, a 3-methoxy carbonylphenyloxy group and thelike; an acylamino group such as an acetamide group, a benzamide group,a 4-(3-t-butyl-4-hydroxy phenoxy)butane amide group and the like; analkylamino group such as a methylamino group, a butylamino group, adiethylamino group, a methyl butylamino group and the like; an arylamino group such as a phenyl amino group, a 2-chloroanilino group andthe like; an ureido group such as a phenylureido group, a methylureidogroup, an N,N-dibutylureido group and the like; a sulfamoyl amino groupsuch as an N,N-dipropyl sulfamoyl amino group and the like; an alkylthio group such as a methyl thio group, an octyl thio group, a2-phenoxyethyl thio group and the like; an aryl thio group such as aphenyl thio group, a 2-butoxy-5-t-octylphenyl thio group, a 2-carboxyphenyl thio group and the like; an alkyloxy carbonyl amino group such asa methoxy carbonyl amino group and the like; an alkyl sulfonyl aminogroup such as a methyl sulfonyl amino group and the like; an arylsulfonyl amino group such as a phenyl sulfonyl amino group, a p-toluenesulfonyl amino group and the like; a carbamoyl group such as an N-ethylcarbamoyl group, an N,N-dibutyl carbamoyl group and the like; asulfamoyl group such as an N-ethyl sulfamoyl group, an N,N-dipropylsulfamoyl group, an N-phenyl sulfamoyl group and the like; a sulfonylgroup such as a methyl sulfonyl group, an octyl sulfonyl group, a phenylsulfonyl group, a p-toluene sulfonyl group and the like; an alkyloxycarbonyl group such as a methoxy carbonyl group, a butyloxy carbonylgroup and the like; a heterocyclic oxy group such as a1-phenyltetrazol-5-oxy group, a 2-tetrahydropyranyloxy group and thelike; an azo group such as a phenylazo group, a 4-methoxyphenyl azogroup, a 4-pivaloylamino phenylazo group, a 2-hydroxy-4-propanoylphenylazo group and the like; an acyloxy group such as an acetoxy groupand the like; a carbamoyloxy group such as an N-methyl carbamoyloxygroup, an N-phenylcarbamoyloxy group and the like; a silyloxy group suchas a trimethyl silyloxy group, a dibutyl methyl silyloxy group and thelike; an aryloxy carbonyl amino group such as a phenoxy carbonyl aminogroup and the like; an imido group such as an N-succinimido group, anN-phthalimido group and the like; a heterocyclic thio group such as a2-benzothiazolyl thio group, a 2,4-di-phenoxy-1,3,5-triazole-6-thiogroup, a 2-pyridylthio group and the like; a sulfinyl group such as a3-phenoxypropyl sulfinyl group and the like; a phosphonyl group such asa phenoxy phosphonyl group, an octyloxy phosphonyl group, a phenylphosphonyl group and the like; an aryloxy carbonyl group such as aphenoxy carbonyl group and the like; an acyl group such as an acetylgroup, a 3-phenyl propanoyl group, a benzoyl group and the like; andionic hydrophilic groups such as a carboxyl group, a sulfo group,phosphono group, a quaternary ammonium group and the like. With respectto the alkyl group, the aralkyl group, the alkenyl group, the alkynylgroup, the cycloalkyl group, and the cycloalkenyl group, which are thesubstituent of the substituted alkyl group, those having branched chainsare preferable because they improve the solubility of the dye and thestability of the ink; and those having asymmetric carbons areparticularly preferred. Out of these, a hydroxy group, an alkoxy group,a cyano group, a halogen atom, a sulfo group (which may also be in theform of a salt) or a carboxyl group (which may also be in the form of asalt) is preferred.

The cycloalkyl groups include a substituted or unsubstituted cycloalkylgroup. The substituted or unsubstituted cycloalkyl group may be acycloalkyl group having 5 to 30 carbon atoms. Examples of thesubstituent of the substituted cycloalkyl group include the substituentsdescribed for the substituted alkyl group. Examples of the cycloalkylgroup include a cyclohexyl group, a cyclopentyl group, a 4-n-dodecylcyclohexyl group and the like.

The aralkyl groups include a substituted or unsubstituted aralkyl group.The substituted or unsubstituted aralkyl group may be an aralkyl grouphaving 7 to 30 carbon atoms. Examples of the substituent of thesubstituted aralkyl group include the substituents described for thesubstituted alkyl group. Examples of the aralkyl group include a benzylgroup, a 2-phenethyl group and the like.

The alkenyl groups include a straight-chain, branched, or cyclicsubstituted or unsubstituted alkenyl group. A substituted orunsubstituted alkenyl group may have 2 to 30 carbon atoms. Examples ofthe substituent of the substituted alkenyl group include thesubstituents described for the substituted alkyl group. Examples of thealkenyl group include a vinyl group, an allyl group, a prenyl group, ageranyl group, an oleyl group, a 2-cyclopenten-1-yl group, a2-cyclohexen-1-yl group and the like.

The alkynyl groups are a substituted or unsubstituted alkynyl grouphaving 2 to 30 carbon atoms. Examples of the substituent of thesubstituted alkynyl group include the substituents described for thesubstituted alkyl group. Examples of the alkynyl group include anethynyl group, a propargyl group and the like.

The aryl groups are a substituted or unsubstituted aryl group having 6to 30 carbon atoms. Examples of the aryl group include a phenyl group, ap-tolyl group, a naphthyl group, an m-chlorophenyl group, ano-hexadecanoyl aminophenyl group and the like. Examples of thesubstituent of the substituted aryl group include the substituentsdescribed for the substituted alkyl group.

The heterocyclic groups are a monovalent group obtained by removing onehydrogen atoms from a 5- or 6-membered substituted or unsubstituted,aromatic or nonaromatic heterocyclic compound, which may also be furthercondensed. A 5- or 6-membered aromatic heterocyclic group may have 3 to30 carbon atoms. Examples of the substituent of the substitutedheterocyclic group include the substituents described for thesubstituted alkyl group. Examples of the heterocyclic group include,with no limitation on substitution site, a pyridine group, a pyrazinegroup, a pyridazine group, a pyrimidine group, a triazine group, aquinoline group, an isoquinoline group, a quinazoline group, a cinnolinegroup, a phthalazine group, a quinoxaline group, a pyrrole group, anindole group, a furan group, a benzofuran group, a thiophene group, abenzothiophene group, a pyrazole group, an imidazole group, abenzimidazole group, a triazole group, an oxazole group, a benzoxazolegroup, a thiazole group, a benzothiazole group, an isothiazole group, abenzisothiazole group, a thiadiazole group, an isoxazole group, abenzisoxazole group, a pyrrolidine group, a piperidine group, apiperazine group, an imidazolidine group, a thiazoline group and thelike.

The alkoxy groups include a substituted or unsubstituted alkoxy group.The substituted or unsubstituted alkoxy group may be an alkoxy grouphaving 1 to 30 carbon atoms. Examples of the substituent of thesubstituted alkoxy group include the substituents described for thesubstituted alkyl group. Examples of the alkoxy group include a methoxygroup, an ethoxy group, an isopropoxy group, an n-octyloxy group, amethoxyethoxy group, a hydroxyethoxy group, a 3-carboxy propoxy groupand the like.

The aryloxy groups may be a substituted or unsubstituted aryloxy grouphaving 6 to 30 carbon atoms. Examples of the substituent of thesubstituted aryloxy group include the substituents described for thesubstituted alkyl group. Examples of the aryloxy group include a phenoxygroup, a 2-methyl phenoxy group, a 4-t-butyl phenoxy group, a 3-nitrophenoxy group, a 2-tetradecanoyl amino phenoxy group and the like.

The silyloxy groups may be a silyloxy group having 3 to 20 carbon atoms.Examples of the silyloxy group include a trimethyl silyloxy group, at-butyldimethyl silyloxy group and the like.

The heterocyclic oxy groups may be a substituted or unsubstitutedheterocyclic oxy group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted heterocyclic oxy group include thesubstituents described for the substituted alkyl group. Examples of theheterocyclic oxy group include a 1-phenyltetrazol-5-oxy group, a2-tetrahydropyranyloxy group and the like.

The acyloxy groups may be a formyloxy group, a substituted orunsubstituted alkyl carbonyloxy group having 2 to 30 carbon atoms, or asubstituted or unsubstituted aryl carbonyloxy group having 6 to 30carbon atoms. Examples of the substituent of the substituted alkylcarbonyloxy group or the substituted aryl carbonyloxy group includesubstituents described for the substituted alkyl group. Examples of theacyloxy group include a formyloxy group, an acetyloxy group, apivaloyloxy group, a stearoyloxy group, a benzoyloxy group, ap-methoxyphenyl carbonyloxy group and the like.

The carbamoyloxy groups may be a substituted or unsubstitutedcarbamoyloxy group having 1 to 30 carbon atoms. Examples of thesubstituent of the substituted carbamoyloxy group include thesubstituents described for the substituted alkyl group. Examples of thecarbamoyloxy group include an N,N-dimethyl carbamoyloxy group, anN,N-diethyl carbamoyloxy group, a morpholino carbonyloxy group, anN,N-di-n-octyl amino carbonyloxy group, an N-n-octyl carbamoyloxy groupand the like.

The alkoxy carbonyloxy groups may be a substituted or unsubstitutedalkoxy carbonyloxy group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted alkoxy carbonyloxy group include thesubstituents described for the substituted alkyl group. Examples of thealkoxy carbonyloxy group include a methoxy carbonyloxy group, an ethoxycarbonyloxy group, a t-butoxy carbonyloxy group, an n-octyl carbonyloxygroup and the like.

The aryloxy carbonyloxy groups may be a substituted or unsubstitutedaryloxy carbonyloxy group having 7 to 30 carbon atoms. Examples of thesubstituent of the substituted aryloxy carbonyloxy group include thesubstituents described for the substituted alkyl group. Examples of thearyloxy carbonyloxy group include a phenoxy carbonyloxy group, ap-methoxyphenoxy carbonyloxy group, a p-n-hexadecyloxy phenoxycarbonyloxy group and the like.

The amino groups may be a substituted or unsubstituted alkylamino grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted arylaminogroup having 6 to 30 carbon atoms. Examples of the substituent of thesubstituted alkylamino group and the substituted arylamino group includethe substituents described for the substituted alkyl group. Examples ofthe amino group include an amino group, a methylamino group, adimethylamino group, an aniline group, an N-methyl-anilino group, adiphenyl amino group, a hydroxyethylamino group, a carboxyethylaminogroup, a sulfoethylamino group, a 3,5-dicarboxy aniline group and thelike.

The acylamino groups may be a formyl amino group, a substituted orunsubstituted alkyl carbonyl amino group having 1 to 30 carbon atoms, ora substituted or unsubstituted aryl carbonyl amino group having 6 to 30carbon atoms. Examples of the substituent of the substituted alkylcarbonyl amino group and the substituted aryl carbonyl amino groupinclude the substituents described for the substituted alkyl group.Examples of the acylamino group include a formylamino group, anacetylamino group, a pivaloylamino group, a lauroylamino group, abenzoylamino group, a 3,4,5-tri-n-octyloxyphenyl carbonyl amino groupand the like.

The amino carbonyl amino groups may be a substituted or unsubstitutedamino carbonyl amino group having 1 to 30 carbon atoms. Examples of thesubstituent of the substituted amino carbonyl amino group include thesubstituents described for the substituted alkyl group. Examples of theamino carbonyl amino group include a carbamoylamino group, anN,N-dimethylamino carbonyl amino group, an N,N-diethylamino carbonylamino group, a morpholino carbonyl amino group and the like.

The alkoxy carbonyl amino groups may be a substituted or unsubstitutedalkoxy carbonyl amino group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted alkoxy carbonyl amino group include thesubstituents described for the substituted alkyl group. Examples of thealkoxy carbonyl amino group include a methoxy carbonyl amino group, anethoxy carbonyl amino group, a t-butoxy carbonyl amino group, ann-octadecyloxy carbonyl amino group, an N-methyl-methoxy carbonyl aminogroup and the like.

The aryloxy carbonyl amino groups may be a substituted or unsubstitutedaryloxy carbonyl amino group having 7 to 30 carbon atoms. Examples ofthe substituent of the substituted aryloxy carbonyl amino group includethe substituents described for the substituted alkyl group. Examples ofthe aryloxy carbonyl amino group include a phenoxy carbonyl amino group,a p-chlorophenoxy carbonyl amino group, an m-n-octyloxy phenoxy carbonylamino group and the like.

The sulfamoyl amino groups may be a substituted or unsubstitutedsulfamoyl amino group having 0 to 30 carbon atoms. Examples of thesubstituent of the substituted sulfamoyl amino group include thesubstituents described for the substituted alkyl group. Examples of thesulfamoyl amino groups include a sulfamoyl amino group, anN,N-dimethylamino sulfonyl amino group, an N-n-octylamino sulfonylaminogroup and the like.

The alkyl sulfonyl amino groups may be a substituted or unsubstitutedalkyl sulfonyl amino group having 1 to 30 carbon atoms. Examples of thesubstituent of the substituted alkyl sulfonyl amino group include thesubstituents described for the substituted alkyl group. Examples of thealkyl sulfonyl amino group include a methyl sulfonyl amino group, abutyl sulfonyl amino group and the like.

The aryl sulfonyl amino groups may be a substituted or unsubstitutedaryl sulfonyl amino group having 6 to 30 carbon atoms. Examples of thesubstituent of the substituted aryl sulfonyl amino group include thesubstituents described for the substituted alkyl group. Examples of thearyl sulfonyl amino group include a phenyl sulfonyl amino group, a2,3,5-trichlorophenyl sulfonyl amino group, a p-methyl phenyl sulfonylamino group and the like.

The alkyl thio groups may be a substituted or unsubstituted alkyl thiogroup having 1 to 30 carbon atoms. Examples of the substituent of thesubstituted alkyl thio group include the substituents described for thesubstituted alkyl group. Examples of the alkyl thio group include amethyl thio group, an ethyl thio group, an n-hexadecyl thio group andthe like.

The aryl thio groups may be a substituted or unsubstituted aryl thiogroup having 6 to 30 carbon atoms. Examples of the substituent of thesubstituted aryl thio group include the substituents described for thesubstituted alkyl group. Examples of the aryl thio groups include aphenyl thio group, a p-chlorophenyl thio group, an m-methoxyphenyl thiogroup and the like.

The heterocyclic thio groups may be a substituted or unsubstitutedheterocyclic thio group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted heterocyclic thio group include thesubstituents described for the substituted alkyl group. Examples of theheterocyclic thio groups include a 2-benzothiazolyl thio group, a1-phenyltetrazol-5-ylthio group and the like.

The sulfamoyl groups may be a substituted or unsubstituted sulfamoylgroup having 0 to 30 carbon atoms. Examples of the substituent of thesubstituted sulfamoyl group include the substituents described for thesubstituted alkyl group. Examples of the sulfamoyl groups include anN-ethyl sulfamoyl group, an N-(3-dodecyloxy propyl)sulfamoyl group, anN,N-dimethyl sulfamoyl group, an N-acetyl sulfamoyl group, an N-benzoylsulfamoyl group, an N—(N′-phenyl carbamoyl)sulfamoyl group and the like.

The alkyl sulfinyl groups may be a substituted or unsubstituted alkylsulfinyl group having 1 to 30 carbon atoms. Examples of the substituentof the substituted alkyl sulfinyl group include the substituentsdescribed for the substituted alkyl group. Examples of the alkylsulfinyl groups include a methyl sulfinyl group, an ethyl sulfinyl groupand the like.

The aryl sulfinyl groups may be a substituted or unsubstituted arylsulfinyl group having 6 to 30 carbon atoms. Examples of the substituentof the substituted aryl sulfinyl group include the substituentsdescribed for the substituted alkyl group. Examples of the aryl sulfinylgroups include a phenyl sulfinyl group, a p-methyl phenyl sulfinyl groupand the like.

The alkyl sulfonyl groups may be a substituted or unsubstituted alkylsulfonyl group having 1 to 30 carbon atoms. Examples of the substituentof the substituted alkyl sulfonyl group include the substituentsdescribed for the substituted alkyl group. Examples of the alkylsulfonyl groups include a methyl sulfonyl group, an ethyl sulfonyl groupand the like.

The aryl sulfonyl groups may be a substituted or unsubstituted arylsulfonyl group having 6 to 30 carbon atoms. Examples of the substituentof the substituted aryl sulfonyl group include the substituentsdescribed for the substituted alkyl group. Examples of the aryl sulfonylgroups include a phenyl sulfonyl group, a p-toluene sulfonyl group andthe like.

The acyl groups may be a formyl group, a substituted or unsubstitutedalkyl carbonyl group having 2 to 30 carbon atoms, a substituted orunsubstituted aryl carbonyl group having 7 to 30 carbon atoms, asubstituted or unsubstituted heterocyclic carbonyl group having 4 to 30carbon atoms, bonded to a carbonyl group through a substituted orunsubstituted carbon atom. Examples of the substituent of thesubstituted alkyl carbonyl group, the substituted aryl carbonyl group,and the substituted heterocyclic carbonyl group include the substituentsdescribed for the substituted alkyl group. Examples of the acyl groupsinclude an acetyl group, a pivaloyl group, a 2-chloroacetyl group, astearoyl group, a benzoyl group, a p-n-octyloxy phenyl carbonyl group, a2-pyridyl carbonyl group, a 2-furyl carbonyl group and the like.

The aryloxy carbonyl groups may be a substituted or unsubstitutedaryloxy carbonyl group having 7 to 30 carbon atoms. Examples of thesubstituent of the substituted aryloxy carbonyl group include thesubstituents described for the substituted alkyl group. Examples of thearyloxy carbonyl group include a phenoxy carbonyl group, ano-chlorophenoxy carbonyl group, an m-nitrophenoxy carbonyl group, ap-t-butyl phenoxy carbonyl group and the like.

The alkoxy carbonyl groups may be a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms. Examples of the substituentof the substituted alkoxy carbonyl group include the substituentsdescribed for the substituted alkyl group. Examples of the alkoxycarbonyl group include a methoxy carbonyl group, an ethoxy carbonylgroup, a t-butoxy carbonyl group, an n-octadecyloxy carbonyl group andthe like.

The carbamoyl groups may be a substituted or unsubstituted carbamoylgroup having 1 to 30 carbon atoms. Examples of the substituent of thesubstituted carbamoyl group include the substituents described for thesubstituted alkyl group. Examples of the carbamoyl group include acarbamoyl group, an N-methyl carbamoyl group, an N,N-dimethyl carbamoylgroup, an N,N-di-n-octyl carbamoyl group, an N-(methylsulfonyl)carbamoyl group and the like.

The phosphino groups may be a substituted or unsubstituted phosphinogroup having 2 to 30 carbon atoms. Examples of the substituent of thesubstituted phosphino group include the substituents described for thesubstituted alkyl group. Examples of the phosphino group include adimethyl phosphino group, a diphenyl phosphino group, a methyl phenoxyphosphino group and the like.

The phosphinyl groups may be a substituted or unsubstituted phosphinylgroup having 2 to 30 carbon atoms. Examples of the substituent of thesubstituted phosphinyl group include the substituents described for thesubstituted alkyl group. Examples of the phosphinyl group include aphosphinyl group, a dioctyloxy phosphinyl group, a diethoxy phosphinylgroup and the like.

The phosphinyloxy groups may be a substituted or unsubstitutedphosphinyloxy group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted phosphinyloxy group include thesubstituents described for the substituted alkyl group. Examples of thephosphinyloxy group include a diphenoxy phosphinyloxy group, adioctyloxy phosphinyloxy group and the like.

The phosphinyl amino groups may be a substituted or unsubstitutedphosphinyl amino group having 2 to 30 carbon atoms. Examples of thesubstituent of the substituted phosphinyl amino group include thesubstituents described for the substituted alkyl group. Examples of thephosphinyl amino group include a dimethoxy phosphinyl amino group, adimethylamino phosphinyl amino group and the like.

The silyl groups may be a substituted or unsubstituted silyl grouphaving 3 to 30 carbon atoms. Examples of the substituent of thesubstituted silyl group include the substituents described for thesubstituted alkyl group. Examples of the silyl group include a trimethylsilyl group, a t-butyldimethyl silyl group, a phenyldimethyl silyl groupand the like.

Examples of the azo groups include a phenyl azo group, a 4-methoxyphenylazo group, a 4-pivaloylamino phenyl azo group, a 2-hydroxy-4-propanoylphenyl azo group and the like.

Examples of the imido group include an N-succinimido group, anN-phthalimido group and the like.

In the general formula (1), X₁ and X₂, each independently, represents anelectron attractive group, provided that X₁ and X₂ may be the same ordifferent. Examples of X₁ and X₂ include an acyl group, an acyloxygroup, a carbamoyl group, an alkyloxy carbonyl group, an aryloxycarbonyl group, a cyano group, a nitro group, a dialkyl phosphono group,a diaryl phosphono group, a diaryl phosphinyl group, an alkyl sulfinylgroup, an aryl sulfinyl group, an alkyl sulfonyl group, an aryl sulfonylgroup, a sulfonyloxy group, an acyl thio group, a sulfamoyl group, athiocyanate group, a thiocarbonyl group, an alkyl halide group, analkoxy halide group, an aryloxy halide group, an alkylamino halidegroup, an alkyl thio halide group, an aryl group substituted withanother electron attractive group, a heterocyclic group, a halogen atom,an azo group, a selenocyanate group and the like.

Each of the X₁ and X₂ may be an acyl group having 2 to 12 carbon atoms,an acyloxy group having 2 to 12 carbon atoms, a carbamoyl group having 1to 12 carbon atoms, an alkoxy carbonyl group having 2 to 12 carbonatoms, an aryloxy carbonyl group having 7 to 18 carbon atoms, a cyanogroup, a nitro group, an alkyl sulfinyl group having 1 to 12 carbonatoms, an aryl sulfinyl group having 6 to 18 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, an aryl sulfonyl grouphaving 6 to 18 carbon atoms, a sulfamoyl group having 0 to 12 carbonatoms, an alkyl halide group having 1 to 12 carbon atoms, an alkoxyhalide group having 1 to 12 carbon atoms, an alkyl thio halide grouphaving 1 to 12 carbon atoms, an aryloxy halide group having 7 to 18carbon atoms, an aryl group having 7 to 18 carbon atoms, substitutedwith two or more electron attractive group, and a heterocyclic groupwhich has 1 to 18 carbon atoms, is 5- to 8-membered, and has a nitrogenatom, an oxygen atom, or a sulfur atom.

In the general formula (1), Z₁ and Z₂, each independently, represents ahydrogen atom, a substituted or unsubstituted alkyl group, a substitutedor unsubstituted alkenyl group, a substituted or unsubstituted alkynylgroup, a substituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup, provided that Z₁ and Z₂ may be the same or different. Examples ofthe alkyl group, the alkenyl group, the alkynyl group, the aralkylgroup, the aryl group, and the heterocyclic group are same in the caseof R₁, R₂, Y₁, and Y₂.

In the general formula (1), M represents a hydrogen atom, or a cation.The cation is an alkali metal ion, an ammonium ion, or a quaternaryammonium ion. The cation may be Li, Na, K, NH₄, or NR₄. R is an alkylgroup, or an aryl group, and examples thereof are same in the case ofR₁, R₂, Y₁, and Y₂. Out of these, preferred cation is Li, Na, K, or NH₄.

As for the combination of the preferred substituents of the dyerepresented by the general formula (1), preferred is a compound in whichat least one of various substituents is the preferred group. Morepreferred is a compound in which a larger number of various substituentsare the preferred groups. Most preferred is a compound in which all thesubstituents are the preferred substituents.

The particularly preferred combinations for the dye represented by thegeneral formula (1) include the following (I) to (V).

(I) R₁ and R₂ may be the same or different, preferably a substituted orunsubstituted alkyl group having 1 to 12 carbon atoms, a substituted orunsubstituted aryl group having 6 to 18 carbon atoms, or a substitutedor unsubstituted heterocyclic group having 4 to 12 carbon atoms. Out ofthese, preferred is a straight-chain alkyl group or branched alkyl grouphaving 1 to 8 carbon atoms. Particularly, a secondary or tertiary alkylgroup is preferred, and a t-butyl group is most preferred.

(II) X₁ and X₂, each independently, represents an electron attractivegroup, may be the same or different, preferably a cyano group, an alkylsulfonyl group having 1 to 12 carbon atoms, an aryl sulfonyl grouphaving 6 to 18 carbon atoms, or a sulfamoyl group having 0 to 12 carbonatoms. Out of these, a cyano group, or an alkyl sulfonyl group having 1to 12 carbon atoms is preferred.

(III) Y₁ and Y₂ may be the same or different, preferably a hydrogenatom, a substituted or unsubstituted alkyl group having 1 to 12 carbonatoms, a substituted or unsubstituted aryl group having 6 to 18 carbonatoms, or a substituted or unsubstituted heterocyclic group having 4 to12 carbon atoms. Out of these, a hydrogen atom, a substituted orunsubstituted alkyl group is preferred. A hydrogen atom is mostpreferred.

(IV) Z₁ and Z₂ may be the same or different, preferably a substituted orunsubstituted alkyl group having 1 to 12 carbon atoms, a substituted orunsubstituted aryl group having 6 to 18 carbon atoms, or a substitutedor unsubstituted heterocyclic group having 4 to 12 carbon atoms. Theparticularly preferred substituent is a substituted or unsubstitutedaryl group or a substituted or unsubstituted heterocyclic group. Out ofthese, particularly, a substituted aryl group is preferred.

(V) M is preferably a hydrogen atom, an alkali metal ion, an ammoniumion, or a quaternary ammonium ion. Out of these, a hydrogen atom, Li,Na, K, or NH₄ is preferred.

Examples of the dye represented by the general formula (1) comprisecompounds represented by the following chemical formulae (1-A) to (1-E).In the following chemical formulae (1-A) to (1-E), C₄H₉(t) represents at-butyl group.

An amount of the dye represented by the general formula (1) is notparticularly limited. Inclusion of the dye represented by the generalformula (1) in the first water-based ink makes it possible to improvetoughness such as light resistance and ozone resistance of a recordingmaterial recorded using the first water-based ink. As described above,the amount of the dye represented by the general formula (1) may exceed0 wt % and is equal to or less than about 7 wt % relative to the totalamount of the first water-based ink. Setting the amount of the dyerepresented by the general formula (1) in the aforementioned range makesit possible to obtain a water-based ink good in printing quality andejection stability. The amount of the dye represented by the generalformula (1) is, for example, in the range of about 0.2 wt % to about 5wt %, and in the range of about 1 wt % to about 5 wt %.

The coloring agent may be composed of the dye represented by the generalformula (1) only or may further comprise other dyes and pigments.

The water may be ion-exchange water or purified water. An amount of thewater relative to the total amount of the first water-based ink is, forexample, in the range of about 10 wt % to about 90 wt %, and in therange of about 40 wt % to about 80 wt %. The amount of the water may bea balance of the other components, for example.

As described above, in the first water-based ink, an amount of glycerinis set so as to satisfy the following condition (A).

3.5X−5≦Y1≦3.5X  (A)

-   -   X: an amount of a dye represented by general formula (1)        relative to a total amount of the ink (wt %)    -   Y1: an amount of glycerin relative to a total amount of the ink        (wt %)    -   Inclusion of glycerin in an amount satisfying Y1≦3.5X makes it        possible to obtain a water-based ink good in preservation        stability. Further, because an amount of the glycerin is set so        as to satisfy Y1≧3.5X−5, a water-based ink that is good in        ejection stability may be obtained.    -   The X and Y1 may strictly satisfy the condition (A) or may be        placed at neighborhood of the straight line of Y1=3.5X−5 in        Y1<3.5X−5 and the straight line of Y1=3.5X in Y1>3.5X.

As described above, in the first water-based ink, in a case of X>5/3.5,glycerin may be comprised in the first water-based ink for ink-jetrecording in an amount satisfying the condition (A), and in a case ofX≦5/3.5, glycerin may be comprised in the first water-based ink in anamount satisfying the following condition (B).

0<Y1≦3.5X  (B)

-   -   X: an amount of a dye represented by general formula (1)        relative to a total amount of the ink (wt %)    -   Y1: an amount of glycerin relative to a total amount of the ink        (wt %)    -   In the case of X≦5/3.5, the X and Y1 may strictly satisfy the        condition (B) or may be placed at neighborhood of the straight        line of Y1=3.5X in Y1>3.5X.

As described above, with respect to the first water-based ink, in a caseof X≦5/3.5, glycerin may not be comprised in the first water-based ink.In this manner, in a case where the amount of the dye represented by thegeneral formula (1) is small, a water-based ink may be obtained that isgood in ejection stability and hardly generates the aggregation evenwhen glycerin is not comprised.

The first water-based ink may further comprised water-soluble organicsolvents other than glycerin. However, an amount of the water-solubleorganic solvents should be in a range that does not undermine theadvantage of the present invention. The water-soluble organic solvent isclassified into a humectant and a penetrant. The humectant prevents inkfrom drying at a tip of an ink-jet head, for example. The penetrantadjusts a drying rate of ink on a recording paper, for example.

The humectant is not limited. Examples of the humectant include loweralcohol such as methyl alcohol, ethyl alcohol, n-propyl alcohol,isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcoholand the like; amide such as dimethylformamide, dimethylacetamide and thelike; ketone such as acetone and the like; ketoalcohol such as diacetonealcohol and the like; ether such as tetrahydrofuran, dioxane and thelike; polyalcohol such as polyalkylene glycol, alkylene glycol and thelike; 2-pyrrolidone; N-methyl-2-pyrrolidone;1,3-dimethyl-2-imidazolidinone; and the like. Examples of thepolyalkylene glycol include, without limitation, polyethylene glycol,polypropylene glycol and the like. Examples of the alkylene glycolinclude, without limitation, ethylene glycol, propylene glycol, butyleneglycol, diethylene glycol, triethylene glycol, dipropylene glycol,tripropylene glycol, thiodiglycol, hexylene glycol and the like. Amongthem, polyalcohol such as alkylene glycol is preferable. One of thehumectants may be used alone or two or more of them may be used incombination.

An amount of the humectant is not particularly limited. The amount ofthe humectant relative to the total amount of the first water-based inkis, for example, in the range of about 0 wt % to about 95 wt %, in therange of about 10 wt % to about 80 wt %, and in the range of about 10 wt% to about 50 wt %.

The penetrant is not limited. Examples of the penetrant include glycolether. Examples of the glycol ether include ethylene glycol methylether, ethylene glycol ethyl ether, ethylene glycol propyl ether,diethylene glycol methyl ether, diethylene glycol ethyl ether,diethylene glycol propyl ether, diethylene glycol butyl ether,triethylene glycol methyl ether, triethylene glycol ethyl ether,triethylene glycol propyl ether, triethylene glycol butyl ether,propylene glycol methyl ether, propylene glycol ethyl ether, propyleneglycol propyl ether, propylene glycol butyl ether, dipropylene glycolmethyl ether, dipropylene glycol ethyl ether, dipropylene glycol propylether, dipropylene glycol butyl ether, tripropylene glycol methyl ether,tripropylene glycol ethyl ether, tripropylene glycol propyl ether,tripropylene glycol butyl ether and the like. One of the penetrants maybe used alone or two or more of them may be used in combination.

An amount of the penetrant is, for example, in the range of about 0 wt %to about 20 wt %. Setting of the amount of the penetrant in theaforementioned range makes it possible to obtain suitable penetration ofthe first water-based ink relative to a paper. The amount of thepenetrant may be in the range of about 0.1 wt % to about 15 wt %, and inthe range of about 0.5 wt % to about 10 wt %.

The first water-based ink may further comprise conventionally knownadditives as required. Examples of the additive include a surfactant, aviscosity modifier, a surface tension modifier, and an antifungal agent.Examples of the viscosity modifier include, without limitation,polyvinyl alcohol, cellulose, water-soluble resin and the like.

The first water-based ink may be prepared, for example, by uniformlymixing the coloring agent, water, the water-soluble organic solvent withother added components as required by a conventionally known method, andthen removing insolubles with a filter or the like.

The first water-based ink may be used as a water-based yellow ink, forexample. The first water-based ink may be a water-based ink other than ayellow color by further comprising coloring agents other than the dyerepresented by the general formula (1).

Next, the second water-based ink for ink-jet recording (hereinafter,also may simply be referred to as “second water-based ink” or “secondink”) is explained. The second water-based ink comprises a coloringagent and water. As described above, the coloring agent comprises thedye represented by the general formula (1).

Examples of the dye represented by the general formula (1) are same asthat of the first water-based ink for ink-jet recording.

An amount of the dye represented by the general formula (1) is notparticularly limited. Inclusion of the dye represented by the generalformula (1) in the second water-based ink makes it possible to improvetoughness such as light resistance and ozone resistance of a recordingmaterial recorded using the second water-based ink. As described above,the amount of the dye represented by the general formula (1) may exceed0 wt % and is equal to or less than about 6 wt % relative to the totalamount of the second water-based ink. Setting the amount of the dyerepresented by the general formula (1) in the aforementioned range makesit possible to obtain a water-based ink good in printing quality andejection stability. The amount of the dye represented by the generalformula (1) is, for example, in the range of about 0.2 wt % to about 5wt %, and in the range of about 1.5 wt % to about 5 wt %.

The coloring agent may be composed of the dye represented by the generalformula (1) only or may further comprise other dyes and pigments.

The water and the amount thereof are same as that of the firstwater-based ink described above.

As described above, in the second water-based ink, an amount of ethyleneglycol is set so as to satisfy the following condition (D).

3.5X−5≦Y2≦X+10  (D)

-   -   X: an amount of a dye represented by general formula (1)        relative to a total amount of the ink (wt %)    -   Y2: an amount of ethylene glycol relative to a total amount of        the ink (wt %)    -   Inclusion of ethylene glycol in an amount satisfying Y2≦X+10        makes it possible to obtain a water-based ink good in        preservation stability. Further, because an amount of the        ethylene glycol is set so as to satisfy Y2≧3.5X−5, a water-based        ink that is good in ejection stability may be obtained.    -   The X and Y2 may strictly satisfy the condition (D) or may be        placed at neighborhood of the straight line of Y2=3.5X−5 in        Y2<3.5X−5 and the straight line of Y2=X+10 in Y2>X+10.

As described above, in the second water-based ink, in a case of X>5/3.5,ethylene glycol may be comprised in the second water-based ink in anamount satisfying the condition (D), and in a case of X≦5/3.5, ethyleneglycol may be comprised in the second water-based ink in an amountsatisfying the following condition (E).

0<Y2≦X+10  (E)

-   -   X: an amount of a dye represented by general formula (1)        relative to a total amount of the ink (wt %)    -   Y2: an amount of ethylene glycol relative to a total amount of        the ink (wt %)    -   In the case of X≦5/3.5, the X and Y2 may strictly satisfy the        condition (E) or may be placed at neighborhood of the straight        line of Y2=X+10 in Y2>X+10.

As described above, with respect to the second water-based ink, in acase of X≦5/3.5, ethylene glycol may not be comprised in the secondwater-based ink. In this manner, in a case where the amount of the dyerepresented by the general formula (1) is small, a water-based ink maybe obtained that is good in ejection stability and hardly generates theaggregation even when ethylene glycol is not comprised.

The second water-based ink may comprise water-soluble organic solventsother than ethylene glycol. Examples of the water-soluble organicsolvents other than ethylene glycol are same as the water-solubleorganic solvents other than glycerin in the first water-based ink exceptthat the glycerin is added to the humectant and ethylene glycol isexcluded from the penetrant. An amount of the water-soluble organicsolvents are same as the water-soluble organic solvents in the firstwater-based ink.

The second water-based ink may further comprise conventionally knownadditives as required. Examples of the additive are same as the additivein the first water-based ink.

The second water-based ink may be prepared, for example, by uniformlymixing the coloring agent, water, the water-soluble organic solvent withother added components as required by a conventionally known method, andthen removing insolubles with a filter or the like.

The second water-based ink may be used as a water-based yellow ink, forexample. The second water-based ink may be a water-based ink other thana yellow color by further comprising coloring agents other than the dyerepresented by the general formula (1).

An ink cartridge comprises the first water-based ink or the secondwater-based ink. As a body of the ink cartridge, for example, aconventionally known body may be used.

Next, an ink-jet recording apparatus is explained. The ink-jet recordingapparatus comprises the ink cartridge and an ink ejection unit, and thewater-based ink comprised in the ink cartridge is ejected from the inkejection unit. Other than this, the ink-jet recording apparatus may havethe construction similar to that of a conventionally known ink-jetrecording apparatus.

FIG. 1 shows a construction of an example of the ink-jet recordingapparatus. As shown in FIG. 1, the ink-jet recording apparatus 1comprises four ink cartridges 2, an ink-jet head 3, a head unit 4, acarriage 5, a drive unit 6, a platen roller 7, and a purge unit 8 asmain constructional elements. In the ink-jet recording apparatus 1 ofthis example, the ink-jet head 3 is the ink ejection unit.

The four ink cartridges 2 each comprise water-based inks of yellow,magenta, cyan, and black. For example, the water-based yellow ink is thefirst water-based ink or the second water-based ink. The ink-jet head 3performs printing on a recording material P such as a recording paper.The head unit 4 is provided with the ink-jet head 3. The four inkcartridges 2 and the head unit 4 are mounted to the carriage 5. Thedrive unit 6 reciprocates the carriage 5 in a straight line. The platenroller 7 extends in a reciprocating direction of the carriage 5 andopposes to the ink-jet head 3.

The drive unit 6 comprises a carriage shaft 9, a guide plate 10, a pairof pulleys 11 and 12, and an endless belt 13. The carriage shaft 9 isdisposed at a lower end portion of the carriage 5 and extends inparallel to the platen roller 7. The guide plate 10 is disposed at anupper end portion of the carriage 5 and extends in parallel to thecarriage shaft 9. The pulleys 11 and 12 are disposed in positionscorresponding to both end portions of the carriage shaft 9 and betweenthe carriage shaft 9 and the guide plate 10. The endless belt 13 isstretched between the pulleys 11 and 12.

In the ink-jet recording apparatus 1, as the pulley 11 is rotated innormal and reverse directions by the drive of a carriage motor 101, thecarriage 5 which is connected to the endless belt 13 is reciprocatedlinearly along the carriage shaft 9 and the guide plate 10 in accordancewith the rotation of the pulley 11.

The recording material P is fed from a paper feeding cassette (notshown) positioned on a side of or underneath the ink-jet recordingapparatus 1. The recording material P is introduced between the ink-jethead 3 and the platen roller 7. Then, a predetermined printing isperformed on the recording material P with the ink ejected from theink-jet head 3. The recording material P then is discharged from theink-jet recording apparatus 1. In FIG. 1, a feeding mechanism and adischarging mechanism of the recording material P are not shown.

The purge unit 8 is provided on a side of the platen roller 7. The purgeunit 8 is disposed so as to oppose the ink-jet head 3 when the head unit4 is in a reset position (above the purge unit 8 in this example). Thepurge unit 8 comprises a purge cap 14, a pump 15, a cam 16, and an inkreservoir 17. The purge cap 14 covers a plurality of nozzles (not shown)of the ink-jet head 3 when the head unit 4 is in a reset position. Inthis state, the pump 15 draws poor ink comprising, for example, airbubbles trapped inside the ink-jet head 3, by being driven by the cam16. Thereby a recovery of the ink-jet head 3 is promoted. The drawn poorink is stored in the ink reservoir 17.

A wiper member 20 is provided on the side of platen roller 7 in thepurge unit 8. The wiper member 20 has a spatula shape, and wipes anozzle surface of the ink-jet head 3 in accordance with the movement ofthe carriage 5. In order to prevent the ink from drying, the cap 18covers the plurality of nozzles of the ink-jet head 3 that returns tothe reset position after the completion of printing.

With respect to the ink-jet recording apparatus 1 of this example, thefour ink cartridges 2 are mounted to one carriage 5. However, thepresent invention is not limited thereto. With respect to the ink-jetrecording apparatus of the present invention, the four ink cartridgesmay be mounted to a plurality of carriages. Further, the four inkcartridges may not be mounted to the carriage, but may be provided andfixed in the ink-jet recording apparatus. In this state, for example,the ink cartridge and the head unit mounted to the carriage areconnected via a tube, or the like, and the ink is supplied to the headunit from the ink cartridge.

Next, a method of stabilizing a first water-based ink for ink-jetrecording is explained. The water-based ink comprises a coloring agentand water. The coloring agent comprises a dye represented by the generalformula (1). The ink is stabilized by setting an amount of glycerin soas to satisfy the condition (A) in the ink. The method of stabilizingthe first water-based ink for ink-jet recording may suitably be appliedto stabilization of the first water-based ink for ink-jet recording.

With respect to the method of stabilizing the first water-based ink forink-jet recording, in a case of X>5/3.5, glycerin may be comprised inthe ink in an amount satisfying the condition (A), and in a case ofX≦5/3.5, glycerin may be comprised in the ink in an amount satisfyingthe condition (B).

With respect to the method of stabilizing the first water-based ink forink-jet recording, in a case of X≦5/3.5, glycerin may not be comprisedin the ink. In this manner, in a case where an amount of the dye issmall, the ink is stabilized even when glycerin is not comprised.

The method of stabilizing the first water-based ink for ink-jetrecording further may satisfy the condition (C).

Next, a method of stabilizing a second water-based ink for ink-jetrecording is explained. The water-based ink comprises a coloring agentand water. The coloring agent comprises a dye represented by the generalformula (1). The ink is stabilized by setting an amount of ethyleneglycol so as to satisfy the condition (D) in the ink. The method ofstabilizing the second water-based ink for ink-jet recording maysuitably be applied to stabilization of the second water-based ink forink-jet recording.

With respect to the method of stabilizing the second water-based ink forink-jet recording, in a case of X>5/3.5, ethylene glycol may becomprised in the ink in an amount satisfying the condition (D), and in acase of X≦5/3.5, ethylene glycol may be comprised in the ink in anamount ratio satisfying the condition (E).

With respect to the method of stabilizing the second water-based ink forink-jet recording, in a case of X≦5/3.5, ethylene glycol may not becomprised in the ink. In this manner, in a case where an amount of a dyerepresented by the general formula (1) is small, the ink is stabilizedeven when ethylene glycol is not comprised.

The method of stabilizing the second water-based ink for ink-jetrecording further may satisfy the condition (F).

With respect to the method of stabilizing the first and secondwater-based ink for ink-jet recording, a dye represented by the generalformula (1) may comprise at least one compound selected from the groupconsisting of compounds represented by the chemical formulae (1-A) to(1-E).

EXAMPLES

Examples of the present invention are described together withComparative Examples, which are provided for illustrative purposes only.The present invention is not limited by the following Examples andComparative Examples.

Examples 1 to 18 and Comparative Examples 1 to 19

An ink composition (Tables 1 to 9) was stirred and then mixed.Thereafter, the mixture was filtered with a hydrophilicpolytetrafluoroethylene (PTFE) type membrane filter having a porediameter of 0.2 μm manufactured by ToyoRoshi Kaisha, Ltd. to produceeach water-based ink and thereby obtained the water-based ink ofExamples 1 to 18 and Comparative Examples 1 to 19. In the followingTables 1 to 9, the dyes (1-A) to (1-E), are compounds respectivelyrepresented by the chemical formulae (1-A) to (1-E).

With respect to the water-based ink of each Example and ComparativeExample, (a) aggregation evaluation, (b) preservation stabilityevaluation, and (c) comprehensive evaluation were carried out with thefollowing method.

(a) Aggregation Evaluation

First, as shown in FIG. 2(A), a water-based ink 22 of a black inkcartridge LC10BK manufactured by Brother Industries, Ltd. and awater-based ink 23 of each Example and Comparative Example wererespectively dropped on a glass slide 21 by 3 μL. Next, as shown in FIG.2 (B), both water-based inks were brought into contact by covering thedropped water-based inks with a cover glass 24. An interface 25 of theboth water-based inks in a prepared slide that is made in theaforementioned manner was observed with a microscope and evaluatedaccording to the following Evaluation Criteria. The marked presence ofthe aggregation substance causes an unstable ejection such asunejection, random ejection, or the like, at the time of ink eject froman ink-jet nozzle. Therefore, if the result of this aggregationevaluation is good, it can be judged that a water-based ink is good inejection stability.

Aggregation Evaluation Criteria

G: granulated aggregation substance was found on interface 25 of theboth water-based inks but wall-like aggregation that is formed bysuccession of aggregation substances was not foundNG: wall-like aggregation that is formed by succession of aggregationsubstances was found on interface 25 of the both water-based inks

(b) Preservation Stability Evaluation

The water-based ink of each Example and Comparative Example was dilutedwith purified water by 1600 times. Absorption of the dilution atwavelength of 440 nm was measured using anultraviolet-visible-near-infrared spectrophotometer, UV3600,manufactured by Shimadzu Corporation. The measurement was carried outusing a measurement cell with a length of 10 mm. Subsequently, thewater-based ink was contained in a sealed container and stored for aweek under an environment of 70° C., separately. Next, the water-basedink after storage was diluted with purified water by 1600 times andabsorption of the dilution was measured in the same manner as thewater-based ink before storage. Then, an absorption reduction rate (%)was obtained with the following formula (I) and preservation stabilitywas evaluated according to the following Evaluation Criteria. When theabsorption reduction rate is low, degradation of the dye is inhibited,and it can be said that the water-based ink is good in preservationstability.

Absorption reduction rate(%)=((X−Y)/X)×100  (I)

X: Absorption before storageY: Absorption after storage

Preservation Stability Evaluation Criteria

G: absorption reduction rate is less than 5%NG: absorption reduction rate is 5% or more

(c) Comprehensive Evaluation

With respect to the water-based ink of each Example and ComparativeExample, from the results of (a) and (b), the comprehensive evaluationwas carried out according to the following Evaluation Criteria.

Comprehensive Evaluation Criteria

G: all evaluation results were “G”NG: “NG” was found in one or more of the evaluation results

Ink compositions and evaluation results of the water-based ink of eachExample are summarized in Tables 1 to 4. Further, ink compositions andevaluation results of the water-based ink of each Comparative Exampleare summarized in Tables 5 to 9. A relationship between an amount of thedye represented by the general formula (1) [X (wt %)] and an amount ofglycerin [Y1 (wt %)] relative to the total amount of ink in Examples 1to 9 and Comparative Examples 1 to 11 is shown in FIG. 3. A relationshipbetween an amount of the dye represented by the general formula (1) [X(wt %)] and an amount of ethylene glycol [Y2 (wt %)] relative to thetotal amount of ink in Examples 10 to 18 and Comparative Examples 12 to19 is shown in FIG. 4.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 INK COMPO-SITION (wt %) dye (X) dye(1-A) 2.7 — — — — dye(1-B) — 2.7 — — — dye(1-C)— — 3.0 — — dye(1-D) — — — 3.0 — dye(1-E) — — — — 1.0 Glycerin 5.1 8.57.6 6.1 — (Y1) Triethylene 3.0 3.0 3.0 3.0 3.0 glycol- n-butyl etherPolyethylene 14.9  11.5  12.4  13.9  20.0  glycol 200 Water BalanceBalance Balance Balance Balance EVALUA- TION Aggregation G G G G GEvaluation Preservation G G G G G Stability Evaluation Absorption 3.2%3.5% 2.9% 2.0% 0.8% reduction rate Compre- G G G G G hensive Evaluation

TABLE 2 Example 6 Example 7 Example 8 Example 9 INK COMPOSITION (wt %)dye (X) dye(1-A) 1.4 — — — dye(1-B) — 4.5 — — dye(1-C) — — 4.0 —dye(1-D) — — — 5.0 Glycerin (Y1) — 11.0  13.0  17.0  Triethylene glycol-3.0 3.0 3.0 3.0 n-butyl ether Polyethylene 20.0  9.0 7.0 3.0 glycol 200Water Balance Balance Balance Balance EVALUATION Aggregation G G G GEvaluation Preservation G G G G Stability Evaluation Absorption 1.2%4.0% 4.5% 4.6% reduction rate Comprehensive G G G G Evaluation

TABLE 3 Example Example Example Example Example 10 11 12 13 14 INKCOMPO- SITION (wt %) dye (X) dye(1-A) 2.7 — — — — dye(1-B) — 3.0 — — —dye(1-C) — — 3.0 — — dye(1-D) — — — 4.5 — dye(1-E) — — — — 4.0 Ethylene8.5 12.3  6.1 11.0  13.0  glycol (Y2) Triethylene 3.0 3.0 3.0 3.0 3.0glycol- n-butyl ether Polyethylene 11.5  7.7 13.9  9.0 7.0 glycol 200Water Balance Balance Balance Balance Balance EVALUA- TION Aggregation GG G G G Evaluation Preservation G G G G G Stability EvaluationAbsorption 3.8% 4.5% 2.0% 3.0% 4.8% reduction rate Compre- G G G G Ghensive Evaluation

TABLE 4 Example Example Example Example 15 16 17 18 INK COMPOSITION (wt%) dye (X) dye(1-A) 2.0 — — — dye(1-B) — 1.5 — — dye(1-C) — — 1.7 —dye(1-D) — — — 1.7 Ethylene glycol (Y2) 11.0  10.0  2.0 6.0 Triethyleneglycol- 3.0 3.0 3.0 3.0 n-butyl ether Polyethylene 9.0 10.0  18.0  14.0 glycol 200 Water Balance Balance Balance Balance EVALUATION AggregationG G G G Evaluation Preservation G G G G Stability Evaluation Absorption3.4% 3.9% 3.9% 3.3% reduction rate Comprehensive G G G G Evaluation

TABLE 5 Compara- Compara- Compara- tive tive tive Comparative Example 1Example 2 Example 3 Example 4 INK COMPOSITION (wt %) dye (X) dye(1-A)2.7 — — — dye(1-B) — 2.7 — — dye(1-C) — — 2.7 — dye(1-D) — — — 2.5Glycerin (Y1) — 1.7 3.4 23.3  Triethylene glycol- 3.0 3.0 3.0 3.0n-butyl ether Polyethylene 20.0  18.3  16.6  — glycol 200 Water BalanceBalance Balance Balance EVALUATION Aggregation NG NG NG G EvaluationPreservation G G G NG Stability Evaluation Absorption 1.0% 3.4% 2.9%5.6% reduction rate Comprehensive NG NG NG NG Evaluation

TABLE 6 Compara- Compara- Compara- tive tive tive Comparative Example 5Example 6 Example 7 Example 8 INK COMPOSITION (wt %) dye (X) dye(1-A) —1.5 — — dye(1-B) — — 2.0 — dye(1-C) — — — 3.5 dye(1-E) 3.0 — — —Glycerin (Y1) 12.3  6.0 8.5 4.0 Triethylene glycol- 3.0 3.0 3.0 3.0n-butyl ether Polyethylene 7.7 14.0  11.5  16.0  glycol 200 WaterBalance Balance Balance Balance EVALUATION Aggregation G G G NGEvaluation Preservation NG NG NG G Stability Evaluation Absorption 5.3%5.4% 5.3% 3.0% reduction rate Comprehensive NG NG NG NG Evaluation

TABLE 7 Comparative Comparative Comparative Example 9 Example 10 Example11 INK COMPOSITION (wt %) dye (X) dye(1-D) 4.5 — — dye(1-E) — 4.0 5.0Glycerin (Y1) 7.0 16.0  20.0  Triethylene glycol- 3.0 3.0 3.0 n-butylether Polyethylene 13.0  4.0 — glycol 200 Water Balance Balance BalanceEVALUATION Aggregation NG G G Evaluation Preservation G NG NG StabilityEvaluation Absorption 3.6% 6.0% 6.2% reduction rate Comprehensive NG NGNG Evaluation

TABLE 8 Compara- Compara- Compara- tive tive tive Example ExampleExample Comparative 12 13 14 Example 15 INK COMPOSITION (wt %) dye (X)dye(1-A) 2.7 — — — dye(1-B) — 2.7 — — dye(1-C) — — 2.7 — dye(1-D) — — —3.5 Ethylene glycol (Y2) 1.7 3.4 20.0  5.0 Triethylene glycol- 3.0 3.03.0 3.0 n-butyl ether Polyethylene 18.3  16.6  — 15.0  glycol 200 WaterBalance Balance Balance Balance EVALUATION Aggregation NG NG G NGEvaluation Preservation G G NG G Stability Evaluation Absorption 3.4%1.8% 5.7% 3.0% reduction rate Comprehensive NG NG NG NG Evaluation

TABLE 9 Compara- Compara- Compara- tive tive tive Example ExampleExample Comparative 16 17 18 Example 19 INK COMPOSITION (wt %) dye (X)dye(1-A) — 4.0 — — dye(1-B) — — 1.5 — dye(1-C) — — — 5.0 dye(1-E) 4.5 —— — Ethylene glycol (Y2) 9.0 16.0  12.5  17.0  Triethylene glycol- 3.03.0 3.0 3.0 n-butyl ether Polyethylene 11.0  4.0 7.5 3.0 glycol 200Water Balance Balance Balance Balance EVALUATION Aggregation NG G G GEvaluation Preservation G NG NG NG Stability Evaluation Absorption 3.6%6.1% 5.2% 5.5% reduction rate Comprehensive NG NG NG NG Evaluation

Examples 1 to 9 and Comparative Examples 1 to 11 Comprising Glycerin

As summarized in Tables 1 and 2, each water-based ink of Examples 1 to 9was good in both results of the aggregation evaluation and thepreservation stability evaluation. In contrast, each water-based ink ofComparative Examples 1 to 3, 8, and 9 that satisfies Y1<3.5X−5 was goodin the result of the preservation stability evaluation but inferior inthe result of the aggregation evaluation. Further, each water-based inkof Comparative Examples 4 to 7, 10, and 11 that satisfies Y1>3.5X wasgood in the result of the aggregation evaluation but inferior in theresult of the preservation stability evaluation.

Examples 10 to 18 and Comparative Examples 12 to 19 Comprising EthyleneGlycol

As summarized in Tables 3 and 4, each water-based ink of Examples 10 to18 was good in both results of the aggregation evaluation and thepreservation stability evaluation. In contrast, each water-based ink ofComparative Examples 12, 13, 15, and 16 that satisfies Y2<3.5X−5 wasgood in the result of the preservation stability evaluation but inferiorin the result of the aggregation evaluation. Further, each water-basedink of Comparative Examples 14, 17, 18 and 19 that satisfies Y2>X+10 wasgood in the result of the aggregation evaluation but inferior in theresult of the preservation stability evaluation.

It will be obvious to those having skill in the art that many changesmay be made in the above-described details of the particular aspectsdescribed herein without departing from the spirit or scope of theinvention as defined in the appended claims.

1. A water-based ink for ink-jet recording comprising a coloring agentand water, wherein the coloring agent comprises a dye represented by thefollowing general formula (1), and in the ink, an amount of glycerin isset so as to satisfy the following condition (A):3.5X−5≦Y1≦3.5X  (A) X: an amount of a dye represented by general formula(1) relative to a total amount of the ink (wt %) Y1: an amount ofglycerin relative to a total amount of the ink (wt %) wherein the amountof glycerin relative to a total amount of the ink (Y1) is 8.5 wt % orlower;

wherein in the general formula (1), R₁, R₂, Y₁, and Y₂ each represents amonovalent group, provided that R₁, R₂, Y₁, and Y₂ may be the same ordifferent; X₁ and X₂, each independently, represents an electronattractive group, provided that X₁ and X₂ may be the same or different;Z₁ and Z₂, each independently, represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted alkynyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that Z₁and Z₂ may be the same or different; and M represents a hydrogen atom ora cation.
 2. The water-based ink according to claim 1, wherein in a caseof X>5/3.5, glycerin is comprised in the ink in an amount satisfying thecondition (A), and in a case of X≦5/3.5, glycerin is comprised in theink in an amount satisfying the following condition (B):0<Y1≦3.5X  (B) X: an amount of a dye represented by general formula (1)relative to a total amount of the ink (wt %) Y1: an amount of glycerinrelative to a total amount of the ink (wt %).
 3. The water-based inkaccording to claim 1, wherein in a case of X≦5/3.5, glycerin is notcomprised in the ink.
 4. The water-based ink according to claim 1,wherein the ink further satisfies the following condition (C): (C) anamount of a dye represented by general formula (1) exceeds 0 wt % and isequal to or less than about 7 wt % relative to a total amount of theink.
 5. The water-based ink according to claim 1, wherein the ink is awater-based yellow ink.
 6. A water-based ink for ink-jet recordingcomprising a coloring agent and water, wherein the coloring agentcomprises a dye represented by the following general formula (1), and inthe ink, an amount of ethylene glycol is set so as to satisfy thefollowing condition (D):3.5X−5≦Y2≦X+10  (D) X: an amount of a dye represented by general formula(1) relative to a total amount of the ink (wt %) Y2: an amount ofethylene glycol relative to a total amount of the ink (wt %)

wherein in the general formula (1), R₁, R₂, Y₁, and Y₂ each represents amonovalent group, provided that R₁, R₂, Y₁, and Y₂ may be the same ordifferent; X₁ and X₂, each independently, represents an electronattractive group, provided that X₁ and X₂ may be the same or different;Z₁ and Z₂, each independently, represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted alkynyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that Z₁and Z₂ may be the same or different; and M represents a hydrogen atom ora cation.
 7. The water-based ink according to claim 6, wherein in a caseof X>5/3.5, ethylene glycol is comprised in the ink in an amountsatisfying the condition (D), and in a case of X≦5/3.5, ethylene glycolis comprised in the ink in an amount satisfying the following condition(E):0<Y2≦X+10  (E) X: an amount of a dye represented by general formula (1)relative to a total amount of the ink (wt %) Y2: an amount of ethyleneglycol relative to a total amount of the ink (wt %).
 8. The water-basedink according to claim 6, wherein in a case of X≦5/3.5, ethylene glycolis not comprised in the ink.
 9. The water-based ink according to claim6, wherein the ink further satisfies the following condition (F): (F) anamount of a dye represented by general formula (1) exceeds 0 wt % and isequal to or less than about 6 wt % relative to a total amount of theink.
 10. The water-based ink according to claim 6, wherein the ink is awater-based yellow ink.
 11. An ink cartridge comprising the water-basedink according to claim
 1. 12. An ink cartridge comprising thewater-based ink according to claim
 6. 13. An ink-jet recording apparatuscomprising the ink cartridge according to claim 11 and an ink ejectionunit, wherein a water-based ink comprised in the ink cartridge isejected from the ink ejection unit.
 14. An ink-jet recording apparatuscomprising the ink cartridge according to claim 12 and an ink ejectionunit, wherein a water-based ink comprised in the ink cartridge isejected from the ink ejection unit.
 15. A method of stabilizing awater-based ink for ink-jet recording comprising a coloring agent andwater, wherein the coloring agent comprises a dye represented by thefollowing general formula (1), and the ink is stabilized by setting anamount of glycerin so as to satisfy the following condition (A) in theink:3.5X−5≦Y1≦3.5X  (A) X: an amount of a dye represented by general formula(1) relative to a total amount of the ink (wt %) Y1: an amount ofglycerin relative to a total amount of the ink (wt %) wherein the amountof glycerin relative to a total amount of the ink (Y1) is 8.5 wt % orlower;

wherein in the general formula (1), R₁, R₂, Y₁, and Y₂ each represents amonovalent group, provided that R₁, R₂, Y₁ and Y₂ may be the same ordifferent; X₁ and X₂, each independently, represents an electronattractive group, provided that X₁ and X₂ may be the same or different;Z₁ and Z₂, each independently, represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted alkynyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that Z₁and Z₂ may be the same or different; and M represents a hydrogen atom ora cation.
 16. A method of stabilizing a water-based ink for ink-jetrecording comprising a coloring agent and water, wherein the coloringagent comprises a dye represented by the following general formula (1),and the ink is stabilized by setting an amount of ethylene glycol so asto satisfy the following condition (D) in the ink:3.5X−5≦Y2≦X+10  (D) X: an amount of a dye represented by general formula(1) relative to a total amount of the ink (wt %) Y2: an amount ofethylene glycol relative to a total amount of the ink (wt %)

wherein in the general formula (1), R₁, R₂, Y₁, and Y₂ each represents amonovalent group, provided that R₁, R₂, Y₁, and Y₂ may be the same ordifferent; X₁ and X₂, each independently, represents an electronattractive group, provided that X₁ and X₂ may be the same or different;Z₁ and Z₂, each independently, represents a hydrogen atom, a substitutedor unsubstituted alkyl group, a substituted or unsubstituted alkenylgroup, a substituted or unsubstituted alkynyl group, a substituted orunsubstituted aralkyl group, a substituted or unsubstituted aryl group,or a substituted or unsubstituted heterocyclic group, provided that Z₁and Z₂ may be the same or different; and M represents a hydrogen atom ora cation.